The invention relates to a device for positioning several wire-shaped articles with respect to each other and to methods of positioning several optical fibers by means of this device.
In the use of optical fibers, it is often necessary to position several fibers with respect to each other with a high degree of accuracy. This is the case, for example, in certain wavelength multiplexers/demultiplexers.
Wavelength multiplexing is a technique in which several luminous signals of different wavelengths are caused to travel in the same optical fibers. These signals are each modulated independently of each other so that the transmission capacity of the fiber is increased. When this technique is used, it is necessary to utilize devices (multiplexers) which inject the light emitted by several transmitters (having different wavelengths) into the same optical fiber. It is also necessary to utilize devices (demultiplexers) which separate the different wavelengths of light emitted from the fiber The essential part of these multiplexer/demultiplexer devices is a wavelength dispersive element: a prism, a network, a non-achromatic lens.
In the demultiplexer mode of operation, the light beam emitted by the end of the emitting fiber is collimated by a collimator lens. The collimated beam is then dispersed by the dispersive element. At the output of the dispersive element several distinct emerging beams are obtained which are passed to a decollimator lens. Several monochromatic or quasi monochromatic images of the end of the emitting fiber are produced in the focal plane of the decollimator lens.
The receiving fibers are arranged so that the end of each of them coincides with one of the monochromatic images. Thus, the signals separated according to their wavelength are collected in the receiving fibers. With the same device, the multiplexer mode of operation can be realized if the direction of propagation of the light in each of the fibers is reversed.
Irrespective of the chosen mode of operation, it is necessary to arrange the ends of each of the receiving fibers so as to coincide with the position of each of the monochromatic images of the emitting fiber. Each fiber has to be positioned with a high degree of accuracy. For example, in the case of a fiber whose core diameter is 50 .mu.m, the positioning has to be ensured with an accuracy of a few microns.
Among the known devices for positioning and connecting optical fibers is the device described in French Pat. No. 2,411,424. This device uses the usual technique of etching diffraction networks, and it ensures an accurate positioning of the fibers with respect to each other. In this device, a matrix is formed by deposition of a thin metal layer on a support polished to be optically flat. Parallel slots for receiving the are then cut into the metal layer by means of a diamond machine tool provided with interferometer control systems. The cost of such a matrix is of course extraordinarily high.